In response to recent increased interest in global environmental preservation, industrial waste is being effectively utilized, even in cement production facilities.
Since such industrial waste includes volatile components such as chlorine, a demineralizer or the like is required to remove the chlorine. The demineralizer is an apparatus that removes volatile components, such as condensed chlorine, by repeating processes of volatilization and condensation between a cement kiln and a preheater. In detail, chlorine bypass dust is generated by solidification of volatile components, the majority of which are chlorine compounds, by extracting exhaust gas from the kiln end part of the cement kiln and cooling the extracted exhaust gas. Afterwards, the chlorine bypass dust is exhausted out of the system, thereby removing chlorine from the cement kiln.
However, since the chlorine bypass dust produced from the demineralizer includes thallium, which is a useful metal, it is preferable to recover and reuse this thallium.
Therefore, proposed is a method for recovering metals, such as thallium, lead, selenium, and the like, from a cement production process by extracting a portion of cement kiln combustion gas having a temperature ranging from 300 to 900° C. from the cement production process, and collecting dust included in the extracted combustion gas by cooling the extracted combustion gas without removing dust from the same (Patent Document 1). In addition, proposed is a method for extracting exhaust gas having a temperature ranging from 200 to 800° C. from a preheater of a cement production facility and recovering useful metals, such as thallium, lead, cadmium, zinc, mercury, and the like, from the exhaust gas (Patent Document 2).    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2006-347794    [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2007-130565